Fig. 4

a Focal mechanism solution of the 2018 Hokkaido Eastern Iburi earthquake. The diagram is an equal area projection on the lower hemisphere of the focal sphere. Solid and open circles indicate compressional and dilatational first motions, respectively. The black lines indicate the preferred nodal planes, whereas the red lines show 50 mechanisms chosen from the set of acceptable solutions. b Geographical distribution of the polarity data. A cross indicates the epicenter of the main shock